On May 29, 2014, at 11:02 AM, Olivier Charansonney <olivier.charanson...@orange.fr> wrote:
> Hello, > > I would like to extract the value in row 1 corresponding to the maximum in > row 2 > > > > Array W > > [,1] [,2] [,3] [,4] [,5] [,6] [,7] > [,8] [,9] [,10] > > [1,] 651.00000 651.00000 651.00000 651.00000 651.00000 651.00000 651.00000 > 119.00000 78.00000 78.00000 > > [2,] 13.24184 13.24184 13.24184 13.24184 13.24184 13.24184 13.24184 > 16.19418 15.47089 15.47089 > >> valinit<-max(W[2,]) > >> valinit > > [1] 16.19418 > > How to obtain ‘119’ > > Thanks, Hi, Using ?dput can help make it easier for others to recreate your object to test code: > dput(W) structure(c(651, 13.24184, 651, 13.24184, 651, 13.24184, 651, 13.24184, 651, 13.24184, 651, 13.24184, 651, 13.24184, 119, 16.19418, 78, 15.47089, 78, 15.47089), .Dim = c(2L, 10L)) W <- structure(c(651, 13.24184, 651, 13.24184, 651, 13.24184, 651, 13.24184, 651, 13.24184, 651, 13.24184, 651, 13.24184, 119, 16.19418, 78, 15.47089, 78, 15.47089), .Dim = c(2L, 10L)) See ?which.max, which returns the index of the *first* maximum in the vector passed to it: > W[1, which.max(W[2, ])] [1] 119 You should consider what happens if there is more than one of the maximum value in the first row and if it might correspond to non-unique values in the second row. Regards, Marc Schwartz ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.